Many types of modern electronic devices, for example, inkjet printers, include some form of fluid dispensing system. Fluid dispensing assemblies generally include structures to take the fluid into the assembly or store it locally and route it to the appropriate output port, an actuator to selectively cause the fluid to exit the output port, and control circuitry to control the selection and activation of the actuator. In some instances, the structures to route the ink to the output port and structures upon which the actuators operate may be contained in a fluid dispensing subassembly.
One exemplary fluid dispensing assembly consists of a print head, either for liquid ink or solid inks that are melted. The print head can include transducers to control dispensation of the ink. These transducers may be electromechanical, microelectromechanical systems (MEMS), acoustic, piezoelectric, etc. The transducer, when activated by an electrical signal, can cause ink to exit the print head through a jet or nozzle. In some examples, when a system activates the transducer with an electrical signal, the transducer actuates and displaces a diaphragm or other structure that in turn causes the ink to pass through the jet onto a printing substrate.
High-voltage linear power amplification is typically used to create the drive waveforms for piezo-electric transducers (PZT) used in some solid ink print heads, as an example of an actuator. These amplifiers (also referred to as waveamps) are optimized for simplicity and low cost to minimize the overall cost of the printer. Often one amplifier drives an entire print head, which may have around a thousand actuator elements. As the technology of printers, print heads, and ink have advanced, the power demands of the actuator waveamps have also increased. These increased power demands have driven research into alternative amplifier architectures with higher efficiency and/or reduced power consumption.
Various alternative techniques have been proposed to improve the efficiency of high-voltage power amplifiers, particularly with respect to audio amplifier applications. Some techniques utilize transistor matching techniques to parallel devices. Other techniques deal with dynamically driven or adaptive power supply rails or driving output devices to one or more intermediate power supply rails to help reduce the power dissipation in the amplifiers. However, these approaches are less desirable for low-cost actuator driver applications, such as those used in printer heads.